Two-particle spin-singlet excitations in coupled spin-1/2 antiferromagnetic alternating chains

摘要

The spectrum of the two-particle spin-singlet (DeltaS(z) = 0, +/-1) excitations of a weakly coupled antiferromagnetic spin-1/2 alternating (J(1) +/- delta) chain is calculated using a mean-field approximation for the interchain exchange (J(2)) by the quantum Monte Carlo method. The bandwidth change of these excitations, the mass gaps in the singlet-singlet excitation spectrum, the top boundaries of the bands and the velocities of these excitations are estimated as functions of the alternating bond delta. The temperatures at which the singlet gaps close are determined. [References: 14]